Luminescence in polynoids II. Different modes of response in the elytra

Abstract

(Text- fig. I) 261 Earlier studies (Nicol, 1953(Nicol, , 1954 showed that two kinds of luminescent responses are produced by electrical stimulation of isolated polynoid scales, viz. brief flashes and a long-lasting glow, the latter frequently being brighter. The brief flashes were regarded as the normal response of the photocytes to nervous excitation, whereas the long glow might be the result of direct excitation of the photocytes. A prolonged glow can usually be evoked by strong shocks (well above threshold). It is sometimes succeeded by rhythmic flashing (Nicol, 1954, fig. IE); alternatively, a series of rhythmic flashes may be succeeded by a prolonged glow (Nicol, 1954, fig. 3A).In the present paper I shall consider the two kinds of responses in more detail. MATERIAL AND METHODSThe species studied were Polynoif scolopendrina, Lagisca extenuata and Gattyana cirrosa; most observations were made on Polynoii. Two kinds of preparations were used. These were isolated elytra, and short sections of worm consisting of a few segments and an elytrum. The material was prepared from worms narcotized with iso-osmotic MgCI2• To induce luminescence electrical stimulation was employed, either condenser discharges or square waves, delivered from an electronic apparatus. The isolated elytrum was placed in a moist chamber over a pair of silver electrodes. To stimulate pieces of the body, silver electrodes were placed on the nerve cord. Luminescent responses were detected with photomultiplier, d.c. amplifier and cathode-ray oscilloscope. Records were made on moving paper. Temperatures were 18°± 1°C. OBSERVATIONS STIMULATION THROUGH THE NERVE CORDThe following observations were made on short sections of worm containing an elytrum, and stimulated via the ventral nerve cord. Polynoif. A single shock sometimes produces one flash, or causes repetitive flashing; or several shocks may be required to elicit the first recordable response. Fast repetitive flashing occurs at frequencies up to Io/sec. 17-2

<p class="HeadingRunIn"><strong>On the morphology of elytra as luminescent organs in scale-worms (Polychaeta, Polynoidae)</strong></p>

“…Our observations confirm that the luminescence in polynoids is characterized by the emission of light flashes or scintillations, which are produced when the animal is irritated, in agreement with Nicol (1953). According to Nicol (1957a), the photocytes occur in a single epithelial layer located in the lower surface of the center of the elytrum (i.e., around the elytrophore). Thus, the light shone through the elytrum, which was clear and non-pigmented over the luminescent tissue.…”

“…In some species of the scale-worm sub-family Polynoinae (Harmothoe Kinberg, 1856) and subfamily Acholoinae (Acholoe Claparède, 1870) an area of the epithelium of the lower surface of the elytra has been reported to emit light flashes upon stimulation. Some other polynoids seem not to be luminescent (e.g., Lepidonotus clava Montagu, 1808, L. squamatus Linnaeus, 1767, Halosydna gelatinosa Sars, 1835, Lepidasthenia argus Hodgson, 1900 (Nicol 1953(Nicol , 1954(Nicol , 1957a(Nicol -c, 1958). In the light-producing species, the lower surface of the elytra has a layer of luminescent cells or photocytes (actually modified epidermal cells), which are lacking in the non-luminescent species (Nicol 1953).…”

Bioluminescence in scale-worm photosomes: the photoprotein polynoidin is specific for the detection of superoxide radicals

“…an area of the epithelium of the lower face ( Fig. 1) emits flashes of light upon stimulation (Nicol 1953(Nicol , 1954(Nicol , 1957a(Nicol ,b,c, 1958. The behavioural function of this bioluminescence remains unknown, and the hypothesis that the signal could be a warning or distracting one has not been demonstrated.…”

A transient intracellular coupling explains the facilitation of responses in the bioluminescent system of scale worms.

“…When stimulated by an electric shock, their basic response is a single flash of green light (19,23), lasting 50-300 ms. When these shocks are repeated, long series of unitary responses can be elicited (22). These emission series exhibit large and remarkably progressive variations, even though the repeated stimuli are maintained at the same threshold value (10).…”